THE YOUNG SCIENTIST. 
23 
terium lunula. Specimens of this object 
may be found in almost any quiet pool of 
clear water. In general, they lie on the 
surface of the mud at the bottom. This 
should be very carefully skimmed, so as to 
disturb it as little as possible, and the col- 
lected water should be placed in a glass 
jar or tumbler, and exposed to the light. 
When the liquid has settled, so that it is 
quite clear, the dipping tube may be used 
to lift a little of the water from a point just 
over the settlings. The dip should be 
placed in a shallow watch glass with a flat 
bottom (a lunette glass) and examined with 
a low or moderate power. It is more 
than likely that several specimens of 
Closteria will be seen moving slowly across 
the field, or lying quietly amongst the 
confervas and debris. Once seen, it will 
never be forgotten. 
Postage Stamps. 
WE again call the attention of our sub- 
sc ibers to the fact, that while we take 
postage stamps of small denominations 
at full value, those of higher denomina- 
tions are of no use whatever to us. We 
cannot sell them, except at a very great 
loss, and the post office will not exchange 
them for smaller denominations. There- 
fore, please do not send them. 
Good News for Young Astronomers. 
AT the suggestion of Prof. Wright we 
have decided to reproduce the Map of 
the Moon, after Baer & Maedler, found in 
" Webb's Celestial Objects," a book which 
is now out of print. The map will be 
twelve inches in diameter, and all the 
principal mountains, seas, etc., will be 
numbered, so that they may be easily re- 
ferred to. Prof. Wright will, during the 
rest of this volume, furnish monthly notes 
on the Geography (if we may use the term) 
of the Moon, and will give the names and 
a description of all its most interesting 
features, as shown on the map. 
This is one of the most interesting de- 
partments of astronomy, and the only 
reason why it has not been more gener- 
ally cultivated is that good maps of the 
moon have not been readily accessible to 
amateurs. 
As this map forms a somewhat ex- 
pensive supplement to such a low-priced 
journal as the Young Scientist, the fol- 
lowing are the conditions upon which it 
will be sent out : To non-subscribers the 
I^rice will be fifty cents per coi^y, and it is 
cheap at this rate ; to all whose names are 
now on our books, and whose subscrip- 
tions are paid for 1880 (at whatever rate), 
it will be sent free. After the issue of this 
number it will be sent only to those 
who pay the full subscription price for the 
Young Scientist— 50 cents per year. It 
will not be sent to those who take the 
Young Scientist at club rates, or where 
a premium is given to the sender of the 
club. The map will be sent out with the 
March number. 
Amateur's Hand-Book. 
TO save disappointment, it may be well 
to notify our readers that the ''Work- 
shop Companion " contains all the matter 
that is found in the "Amateur's Hand- 
Book." Those, therefore, who buy the 
" Workshop Companion " do not need the 
"Hand-Book." 
Work and Luck. 
MOST people like to be astonished and 
to have their faculty of wonder ex- 
cited, and nothing excites this feeling 
more than the contemplation of a result, 
the causes of which do not seem to be suf- 
ficient. When we see, for the first time, 
a weak man raising a heavy weight by 
means of a lever, we are struck with won- 
der, because, it does not seem possible 
that the use of a slender bar can add so 
much to the man's strength, and when we 
see a pressure equal to many tons exerted 
by the forcing in of a little water into a 
cylinder, we have the same feeling. 
W^e all like to see and to hear of wonder- 
ful things. But when we come to under- 
stand the causes which produce the re- 
sults which have astonished us, we no 
longer wonder. We find that in every 
case the cause and the effect are precisely 
equal, and we use levers and hydraulic 
presses without being in the slightest de- 
gree surprised at the effect produced by 
